Calcium Metabolism in Old Age 



113 



It is worth while reporting that the technique used in the 

 above experiments matured in consequence of a great number 

 of experiments in which adaptation (significantly increased 

 absorption) could not be observed. In these earlier experi- 

 ments rats given vitamin D throughout were used. Short 



Age I 30 months 



m^. Ca/day 

 22 T absorbed 



16 



6- 



O 



■4 

 ■8H 



■12 



-293 

 jng. 



0.25 % 

 0.04% 



levels of 

 Ca in the diet 



Fig. 2. The Ca absorption in six old rats given 0-5 I.U. vitamin 



D daily. (Ca intake on the • 25 per cent Ca diet, about 40 mg. 



daily.) 



periods of ten to fourteen days on the • 25 per cent Ca diet 

 were used to test the absorption. In between the rats were 

 given the 0-04 per cent Ca diet for weeks and months. Some 

 suffered losses of 50-100 mg. (2-4 per cent of the total), but 

 this did not result in a clearcut increase of the absorption 

 from the • 25 per cent diet. Other groups of rats very quickly 

 reduced their faecal output to very low values, so that they 

 hardly lost any body Ca at all. 



